The Deoxyribonuclease Induced after Infection of Escherichia coli by Bacteriophage T5

After infection of Escherichia coli, bacteriophage T5 induces an exonuclease which yields oligonucleotides upon hydrolysis of a DNA strand from the 5'-end. A mutant of T5 has been isolated which bears a mutation in the structural gene of the exonuclease. In addition to inducing a heat-labile enzyme, the mutant phage is unable to form plaques at 45°. Single step revertants lose both of these properties. After infection with the mutant at 45° DNA synthesis begins normally but arrests prematurely. The DNA which is synthesized in mutant-infected cells is converted to a rapidly sedimenting form, as is the DNA synthesized in wild type-infected cells. However, there is defective conversion to mature length phage DNA in mutant-infected cells.